This section provides background information related to the present disclosure which is not necessarily prior art.
Sprinkler skipping is a behavior that is sometimes exhibited by an array of sprinklers during a full scale fire. Typically, a fire will initially set off one to four sprinklers in quick succession depending where the ignition source is in relation to the sprinkler array. These first few activations are usually defined as the first ring of activated sprinklers. As hot gas from the fire spreads radially outward from the center, the hot gas comes in contact with the second ring of sprinklers. The second ring of sprinklers are radially adjacent to the first ring. The next consecutive/adjacent ring would be the third ring, and the next would be the fourth ring and so on. Sprinkler skipping occurs when a sprinkler in the third or fourth ring operates before a sprinkler in the second ring. In more general terms, skipping is when a non-activated sprinkler adjacent to a flowing sprinkler fails to operate before sprinklers that are farther away from the heat source. This behavior results in the sprinkler array not performing to its highest efficiency.
Some members of the fire protection industry have concluded that water impingement is the cause of sprinkler skipping. Water impingement is defined as (1) water flow from an activated sprinkler to an adjacent sprinkler; or (2) water droplets carried by the fire plume on to an adjacent sprinkler and impinging on that sprinklers thermal element. The water impingement absorbs heat from the thermal element preventing or retarding its activation (the water keeps the thermal element below its operating temperature).
In order to prevent water impingement, it has been proposed that a shield be installed such that water traveling from a flowing sprinkler or water carried by the fire plume will not strike the thermal element of an adjacent sprinkler. This, in theory, prevents the thermal element from becoming wetted, thereby preventing skipping. The shield that has been proposed is of a solid cylindrical construction.
There is some concern that the response time of the thermal element will be impeded by the skipping shield. The impeded response time can negatively impact the performance of a sprinkler in a fire and in a “Response Time Index” plunge oven test. Both of these tests are important to the performance of the sprinkler in terms of gaining Approvals and Listings.
The present disclosure provides improvements to the design of the skipping shield to reduce the negative impact that the shield has on the thermal response of the sprinkler. By adding holes, slots, louvers, or mesh to the skipping shield, water from the flowing head can still be blocked from impinging on the thermal element. The improved shield will block water from impinging on the heat responsive element but will allow hot gas from the fire to flow through the shield thereby improving the response time of the thermal element.
The present disclosure also provides a geometrical shape other than the cylindrical shape. The improved geometrical shape is designed in such a fashion to encourage laminar or turbulent gas flow around the shield and onto the thermal element of the sprinkler. The shape is made such that water impinges on the shield, yet provides improvement to the airflow that lowers the response time index as compared to that of previous skipping shield designs.
The present disclosure also includes the combination of holes, slots, louver, or mesh with a geometric shape that promotes improved air flow around the thermal element.
Compared to previously proposed skipping shield designs, the improved skipping shield will yield better sprinkler performance in fires by enhancing the response time. The improved skipping shield will also reduce the RTI (Response Time Index) when tested in a plunge oven.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.